Horticultural crops include a diverse array of crops comprising fruits, vegetables, nuts, flowers, aromatic and medicinal plants. They provide nutritional, medicinal, and aesthetic benefits to mankind. However, these crops undergo many biotic (e.g., diseases, pests) and abiotic stresses (e.g., drought, salinity). Conventional breeding strategies to improve traits in crops involve the use of a series of backcrossing and selection for introgression of a beneficial trait into elite germplasm, which is time and resource consuming. Recent new plant breeding tools such as clustered regularly interspaced short palindromic repeats (CRISPR) /CRISPR-associated protein-9 (Cas9) technique have the potential to be rapid, cost-effective, and precise tools for crop improvement. In this review article, we explore the CRISPR/Cas9 technology, its history, classification, general applications, specific uses in horticultural crops, challenges, existing resources, associated regulatory aspects, and the way forward.

A Gram positive, aerobic, and non-spore-forming bacterial strain, 20TX0166 T , was isolated from a diseased onion bulb in Texas, USA. Upon testing its pathogenicity on onion bulb, it produced pathogenic response which makes it rst species of pathogen belonging to the phylum actinobacteria detected in onion. Phylogenetic analysis of the 16S rRNA gene sequence revealed that the strain belonged to the genus Curtobacterium and was most similar to Curtobacterium accumfaciens LMG 3645 T (100%), C. pusillum DSM 20527 T (99.5%), and C. oceanosedimentum ATCC 31317 T (99.5%). The orthologous ANI (orthoANIu), ANI based on blast (ANIb), and dDDH values between the novel strain and the closest relative, C. accumfaciens LMG 3645 T , were 95.7%, 95.4%, and 63.3%, respectively. These values were below the recommended species cut-off threshold of 96% (ANI) and 70% (dDDH), suggesting the strain may be a novel species. The estimated genome size of the novel species was 3.98 Mbp with a G + C content of 70.8%. Physiologic and phenotypic characters of this novel strain were also unique when compared with the closely related species. The major cellular fatty acids of this strain were C 15:0 anteiso and C 17:0 anteiso. Using a polyphasic approach based on phenotypic and genotypic analyses, strain 20TX0166 T represents a novel species of the genus Curtobacterium, and the name Curtobacterium allii sp. nov.

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A Gram-stain-negative, aerobic and non-spore-forming bacterial strain, designated 20TX0172T, was isolated from a rotting onion bulb in Texas, USA. The results of phylogenetic analysis based on the 16S rRNA sequence indicated that the novel strain represented a member of the genus Pseudomonas and had the greatest sequence similarities with Pseudomonas kilonensis 520-20T (99.3 %), Pseudomonas corrugata CFBP 2431T (99.2 %), and Pseudomonas viciae 11K1T (99.2 %) but the 16S rRNA phylogenetic tree displayed a monophyletic clade with Pseudomonas mediterranea CFBP 5447T. In the phylogenetic trees based on sequences of four housekeeping genes (gap1, gltA, gyrB and rpoD), the novel strain formed a separate branch, indicating that the strain was distinct phylogenetically from known species of the genus Pseudomonas . The genome-sequence-derived average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) values between the novel isolate and P. mediterranea DSM 16733T were 86.7 and 32.7 %, respectively. These values were below the accepted species cutoff threshold of 96 % ANI and 70 % dDDH, affirming that the strain represented a novel species. The genome size of the novel species was 5.98 Mbp with a DNA G+C content of 60.8 mol%. On the basis of phenotypic and genotypic characteristics, strain 20TX0172T represents a novel species of the genus Pseudomonas . The name Pseudomonas uvaldensis sp. nov. is proposed. The type strain is 20TX0172T (=NCIMB 15426T=CIP 112022T).